A disk file of the HDA type employing two major assemblies, that is, a head disk assembly and a drive assembly, is shown in U.S. Pat. No. 4,034,411. In addition, disk files employing teachings of the abovereferenced patent, currently being marketed by several companies, are the IBM 3350 type disk file, the Storage Technology 8350 type disk file, and the Memorex 3650 type disk file.
In these files the HDA is arranged with the disks in a horizontal plane so that the disk spindle is vertical. The HDA is positioned on a substantially horizontal baseplate with the disk spindle extending above the baseplate. The baseplate is provided with suitable reference surfaces for the HDA to insure that the axis of the voice coil is coaxial with the annular flux gap of the VCM, which is also attached to the baseplate.
The above type disk files employing HDAs are characterized primarily by the magnetic transducers being permanently associated with corresponding disk surfaces, as distinguished from earlier files employing removable disk packs. In these earlier files, the disk packs merely consisted of a stack of magnetic disks and the magnetic head carriage assembly and the actuator were permanently associated with the drive portion of the file.
The need to increase track densities and to decrease the flying height of the head relative to the disk surface imposed severe tolerance limitations on both the heads and the disk when they were not permanently associated with each other, as in the case of the earlier disk pack-disk drive configuration. To avoid the manufacturing costs which these severe tolerances would impose on a disk pack-disk drive configuration, the prior art suggested the construction of a Data Module where the magnetic heads and the carriage were permanently associated with the disks. A Data Module of this type and its associated disk drive structure is shown in U.S. Pat. No. 3,973,273 (Lissner et al) assigned to the assignee of the present invention. As shown in the Lissner et al patent, the coil of the voice coil motor, which functions to position the magnetic heads to an addressed data track, is permanently associated with the voice coil motor of the drive, and means are provided to automatically couple an extension from the coil to the head carriage assembly when the Data Module is placed on the drive. The Data Module and its associated drive are constructed such that the replacement of the Data Module can be readily accomplished by an unskilled operator, which permits the user to maintain a substantial amount of data offline and, when a particular set of data is required, merely to place that Data Module into the system, much like the use of prior art disk packs.
The cost of maintaining data online, measured in terms of cost per byte, of course decreases as the track density and linear recording density of a disk increases. This decrease in storage cost per byte, plus increase in the ability of a given data processing system to handle data more rapidly and economically, plus the desire by users to add new applications to the data processing system, has encouraged users and system designers to keep more data online, as distinguished from the prior practice of loading offline data into the system via disk pack and data modules. As a result, the prior art has suggested the HDA-drive configuration represented by U.S. Pat. No. 4,034,411, previously referred to.
The HDA, as described therein, is constructed such that the coil of the VCM is permanently associated with the HDA, and apparatus which was on the drive to assist the operator in automatically loading the Data Module has been eliminated from the drive portion of the combination. In such an arrangement, the HDA is still replaceable and the design intent is to make the HDA field replaceable by a service engineer, rather than an operator. An added advantage of such an arrangement is obtained in manufacturing such a file since the HDA assembly contains substantially all of the close tolerance mechanical parts of the file and is generally manufactured in a "clean room" type of environment. The remaining portion of the drive, on the other hand, involves components which can be assembled in more conventional type electronic assembly environments.
While the volume of data stored on a disk file is an important consideration from a data processing system standpoint, another significant consideration is the time it takes to access such data. Access time generally comprises the period it takes the voice coil motor or actuator to perform a seek operation, that is, to move a magnetic head from the current track or cylinder to a new track or cylinder, plus the rotational delay for a particular record located on the recording track to be rotated under the head once the head is positioned over the new track.
Seek times are on the order of 20 to 30 milliseconds in present commercial files, which is still relatively long compared to the time it takes the file to read or write a given record. As a result, from a system standpoint where several different records on different tracks or cylinders are required in sequence, a substantial amount of time is consumed by the seek operations. The system performance can generally be improved if two separate actuators could be provided, each having access to half the amount of data since the seek operations can then be overlapped, thereby reducing the waiting time for the data processing system to the data required to perform its operation.
In some data processing applications, the only available option for a user, where system throughout is limited by seek times, is to add additional files, since that is the only available manner to obtain additional access operations at the current level of access times and magnetic recording densities. This involves more cost for storage and requires more physical space to house the installation.
The prior art has suggested fixed disk multi-actuator files for overlapping access operations to contiguous data sets on the same disk or to the same data sets. Such a configuration is represented by U.S. Pat. No. 3,025,710. However, the configuration of these fixed disk files are such that the replacement of the magnetic disks is not contemplated without a complete dismantling of the file as distinguished from a configuration which employs two separate major assemblies such as the HDA and drive assembly.
The present invention avoids the above-described dismantling problem by providing a compact HDA-drive configuration in which the HDA employs two separate independently operated head carriage assemblies, each of which is associated with a different set of disks and are moved independently of each other by the actuator which is mounted on the drive assembly of the file. The disks are mounted on a common shaft and disposed vertically in the HDA. The use of two separate actuators to access data on a given number of disk surfaces allows the track density of each set of disk surfaces to be increased because smaller carriages can be employed which permits more precise control of the head-arm assemblies associated with each carriage.
The drive portion comprises a baseplate having a generally U-shaped cross-section in the front portion so as to accommodate the lower portion of the HDA, which surrounds the bottom half of the vertically arranged disks. The U-shaped front portion is open to accommodate the lower section of the HDA as it is inserted into the drive in the horizontal direction. The upper edges of the front portion of the U-shaped baseplate are designed to provide means for referencing the HDA to the actuator structure which is mounted on an integral rear platform of the baseplate, thereby allowing the spindle drive motor to be mounted under the flat rear portion of the baseplate which mounts the actuator. The bottom of the U-shaped front portion extends generally upward to the leading edge of the rear platform to provide adequate space for the spindle motor, and to provide additional strength to the baseplate. The motor is pivotally mounted to the bottom of the rear platform of the baseplate with its axis parallel to the disk spindle. The motor is coupled to the disk spindle by means of a pair of pulleys and a drive belt which lie in a plane perpendicular to the disk spindle and motor shaft. The opposite side of the motor shaft drives the blower for the air supply system. The components of the air supply system, such as the absolute filter and ducting from the filter to the HDA, are packaged below the baseplate. The relative replacement of all of the above components contributes to a small, compact disk file arrangement.
The carriages of the HDA are positioned so that the transducers move along a pair of parallel axes which extend normal to the disk shaft and lie in a plane substantially parallel to the referencing plane established by the upper edges of the U-shaped baseplate. The carriages are positioned between the disk spindle axis and the actuator of the drive, which permits the HDA to be loaded into its operating position by movement of the HDA in a horizontal direction parallel to these axes. Such an arrangement permits the HDA to be operatively positioned on the drive by adjusting only a minimum number of components on the drive assembly, such as the electrical connections to the HDA and the drive belt.
It is, therefore, an object of the present invention to provide a compact disk file of the HDA-drive configuration type in which the HDA is provided with two head carriage assemblies which are operated independently from the drive and access different disks mounted on a common shaft.
A further object of the present invention is to provide a compact disk file of the HDA-drive configuration type in which the drive assembly is characterized by a U-shaped baseplate for supporting the HDA with the bottom half of the HDA which surrounds the vertical disks disposed within the U-shaped baseplate.
A still further object of the present invention is to provide a compact disk file comprising vertical disks and two separate head accessing carriages mounted in an HDA which is referenced to a U-shaped baseplate of the drive assembly wherein the spindle drive motor is mounted with its axis parallel to the disk spindle, beneath the magnet structure of the voice coil motor, and in which the blower for the air supply system to the HDA is mounted to the shaft of the spindle drive motor.
Another object of the present invention is to provide a dual carriage HDA assembly in which the carriages move independently along spaced parallel paths extending normal to the disk spindle and are disposed on the same side of the spindle.